Clamping assembly

ABSTRACT

In a clamping assembly having a first component ( 1 ) and a second component ( 2 ), which has an essentially cylindrical outer jacket ( 21 ), is attachable to the first component, has a support surface ( 20 ) supported against the first component ( 1 ) and which is able to be clamped against the first component ( 1 ) via a clamping sleeve ( 3 ) that is slid onto the outer jacket ( 21 ) and can be screwed onto the first component and via a snap ring ( 4 ) that comes to rest against a first clamping shoulder ( 35 ) formed on the inner wall ( 33 ) of the clamping sleeve ( 3 ) and against a second clamping shoulder ( 22 ) formed on the outer jacket ( 21 ) of the second component ( 2 ), it is proposed that the snap ring ( 4 ) be configured as a detent that deflects elastically in a radial direction and that the outer jacket ( 21 ) of the second component ( 2 ) be provided with an undercut ( 24 ) behind the second clamping shoulder ( 22 ), when viewed in the axial direction, into which the elastically deflecting snap ring ( 4 ) is able to be deformed radially inwardly so that the clamping sleeve ( 3 ) may be guided over the snap ring ( 4 ) when slid onto the outer jacket ( 21 ) of the second component ( 2 ) and the snap ring ( 4 ) is able to be brought into engagement in an annular groove ( 31 ) on the inner wall ( 33 ) that is designed as an opposing detent.

BACKGROUND INFORMATION

[0001] The invention relates to a clamping assembly, especially for use on a fuel injector, having the features of the preamble of independent claim 1.

[0002] A clamping assembly of this type is known, for example, from published German patent application 2 303 506 A. The clamping assembly shown there includes as a first component a cylinder head of an internal combustion engine. A fuel injector, representing the second component and having an essentially cylindrically shaped outer cover, has a support surface that rests against the cylinder head in a recess of the same and is clamped in the cylinder head via a clamping sleeve that is designed as a hollow screw and via a snap ring that is set in an annular groove of the fuel injector, for which purpose the clamping sleeve has an external thread that can be screwed into an internal thread of the cylinder head. For this purpose, the clamping sleeve has a recess on its end facing the cylinder head that functions as a first clamping shoulder and in which the snap ring comes to rest when the clamping sleeve is tightened. The section of the annular groove of the fuel injector that faces the cylinder head functions as a second clamping shoulder. The snap ring is clamped between the first and second clamping shoulders upon tightening.

[0003] In the known clamping assembly, the clamping sleeve is slid onto that end of the fuel injector, representing the second component, which faces away from the support surface of the first component and is located behind the snap ring when viewed from the cylinder head. This makes it necessary for the diameter of the second component behind the snap ring to be configured to be smaller than the inner diameter of the clamping sleeve all the way around, so that the clamping sleeve may be slid over the outer jacket without a problem. This part of the outer jacket must therefore have no steps, nor any laterally projecting supports. Moreover, these conditions necessitate increased cutting and deformation effort in the production of the second component. For example, if, in addition, the first component should have an external thread and the clamping sleeve an internal thread that is screwed together with the external thread of the first component, the section of the clamping sleeve provided with the internal thread must be slid over the outer jacket of the second component, which, on the one hand, requires a great amount of play between the internal thread of the clamping sleeve and the outer jacket and, on the other hand, may result in the internal thread of the clamping sleeve being damaged, for example, by pushing against the snap ring.

ADVANTAGES OF THE INVENTION

[0004] In the clamping assembly of the present invention having the characterizing features of claim 1, the clamping sleeve may advantageously be slid, from the end of the second component that faces out toward the support surface of the first component, onto the outer jacket of the second component. Due to the fact that the snap ring is designed as a detent which elastically deflects in the radial direction, and that the second component has an undercut into which the snap ring may deform, and that an annular groove accommodating the snap ring is formed on the inner wall of the clamping sleeve as an opposing detent, the clamping sleeve, when it is slid on, may be slid a bit past the snap ring, until the snap ring, which is elastically pretensioned as a result, snaps into the annular groove of the clamping sleeve, thereby captively mounting the clamping sleeve on the second component. When the clamping sleeve is subsequently screwed together with the first component, the snap ring is drawn out from the undercut and pressed against the clamping shoulder of the second component. The advantage of this is that the threaded section of the clamping sleeve does not have to be pushed over the snap ring. By using the clamping assembly of the present invention, a robust attachment of the two components is advantageously achieved, requiring little assembly effort and also, in particular, little structural space. The components are joined only after complete machining, so that no captive parts have to be handled during the production process.

[0005] Advantageous embodiments and further developments of the invention are made possible via the features included in the dependent claims.

[0006] The fact that the second clamping shoulder is disposed to the side of the support surface and functions as an axial delimitation of an annular groove in the second component, which has a depth that is greater than the wire diameter of the snap ring, and that the annular groove has a stop face for the snap ring opposite the second clamping shoulder, advantageously makes it possible for the snap ring to come to rest against the stop face and automatically deform radially inwardly and into the undercut when the clamping sleeve is slid on.

[0007] It is advantageous for the inner wall of the clamping sleeve to have, at its end that is pressed onto the second component, a peripheral chamfer that facilitates the sliding on of the snap ring. When the clamping sleeve is slid on, the chamfer of the clamping sleeve cooperates with the stop face of the second component in such a manner that the snap ring is deformed so as to slide radially inwardly into the undercut all along the chamfer without the aid of any tools.

[0008] It is especially advantageous for the undercut made on the second component to be formed by an essentially conical surface bordering on the clamping shoulder, since in this case, when the clamping sleeve is screwed together with the first component, the conical surface exercises a centering effect on the snap ring, which is snapped into the clamping sleeve, and on the clamping sleeve itself.

DRAWINGS

[0009] An exemplary embodiment of the invention is illustrated in the drawings and is explained in the following description. Shown are:

[0010]FIG. 1 is a cross-section through the clamping assembly of the present invention that, in the illustrated exemplary embodiment, is disposed on the fuel injector of an internal combustion engine,

[0011]FIG. 2 is a top view of the snap ring,

[0012]FIGS. 3 through 7 show the assembly of the clamping assembly in a simplified representation.

DESCRIPTION OF AN EXEMPLARY EMBODIMENT

[0013]FIG. 1 shows a first exemplary embodiment of a clamping assembly of the present invention. In this exemplary embodiment, the clamping assembly is mounted on a fuel injector for internal combustion engines, a first component 1 of the clamping assembly being formed by the magnet assembly of the fuel injector. Magnet assembly 1 includes a magnetic core having pole face 10 and coil 8, as well as a valve spring 9, which impinges an axially movable armature 7 having a tie plate and tie bolt. A valve assembly of the fuel injector represents a second component 2 of the clamping assembly. Valve assembly 2 has a support surface 20 supported against pole face 10 of magnet assembly 1. A recess 29 in support surface 20 forms an armature compartment to accommodate armature 7. The movable armature controls the discharge of fuel from its control pressure chamber, which in turn controls the injection operation of the fuel injector. As illustrated in FIG. 1, the clamping assembly also includes a clamping sleeve 3 and a snap ring 4.

[0014] As may best be recognized in the simplified representation of FIG. 3, first component 2 has, on a part of its length, a cylindrical outer jacket 21 that does not need to extend over the entire length of component 2. In the exemplary embodiment illustrated here, cylindrical outer jacket section 21 is delimited by a shoulder 28, for example. Close to a support surface 20 of second component 2, an annular groove 27 is introduced in outer jacket 21 of second component 2 so that a narrow section 25 of outer jacket 21 forms a peripheral collar. Starting from collar 25, annular groove 27 forms a second clamping shoulder 22 which is intended to hold a snap ring 4 and which has, adjacent to it, an undercut 24 in the form of a conical surface having a tapered diameter. The conical surface transitions into a short cylindrical face section, which in turn projects from an annular face situated opposite clamping shoulder 22 and running perpendicular to outer jacket 21. Annular face 23 functions as a stop face for snap ring 4.

[0015] Snap ring 4 is illustrated in FIG. 2 and FIG. 3. The snap ring is made out of an elastically deflecting material, especially an elastically flexible metal and, in the preferred exemplary embodiment illustrated here, has a circular wire cross section. However, other cross-sections are also possible. As may best be recognized in FIG. 2, the snap ring has an opening 41. The angle a subtended by opening 41 is dimensioned in such a manner that, on the one hand, snap ring 4 permits radial deflection while clamping sleeve 3 is being mounted (FIG. 5), but that, on the other hand, the support angle (360°−a), that is the angle subtended by the snap ring when it comes to rest against second clamping shoulder 22, is not too small. In a preferred exemplary embodiment, opening angle a is between 40° and 60°. Elastic element snap ring 4 may be bent outward somewhat when being mounted on second component 2 and, using opening 41, be clipped into annular groove 27 of second component 2 or be guided in the axial direction over peripheral collar 25, as is illustrated in FIG. 4. The elasticity of snap ring 4 is calculated to be large enough so that it is not permanently deformed in the course of being positioned on second component 2 and during subsequent deflection into annular groove 27 (FIG. 5). Before clamping sleeve 3 is mounted, snap ring 4 rests against stop face 23 in such a manner that it is radially movable, as is illustrated in FIG. 4.

[0016] As is recognizable in FIG. 1 and FIG. 5, clamping sleeve 3 has a cylindrical inner wall 33 having an internal thread 34. For the sake of simplicity, internal thread 34 is not depicted in FIG. 5. Internal wall 33 of clamping sleeve 3 has an annular groove 31 and a chamfer 32 on the end facing away from internal thread 34. As illustrated in FIG. 5, clamping sleeve 3 is slid from support surface 20 of second component 2 out onto outer jacket 21 until chamfer 32 butts against snap ring 4. When the clamping sleeve is slid further, snap ring 4, which rests against stop face 23, is first elastically compressed, sliding radially inwardly along chamfer 32, and in the process penetrates into undercut 24.

[0017] When clamping sleeve 3 is slid further, snap ring 4, which is elastically pretensioned against inner wall 33, snaps into annular groove 31 on inner wall 33 of clamping sleeve 3, as illustrated in FIG. 6. Snap ring 4 is thus encompassed in a press fit over approximately half of the perimeter by annular groove 31. Clamping sleeve 3 is then captively connected to second component 2. Clamping sleeve 3 may be moved axially back and forth, the axial mobility of clamping sleeve 3 being limited by second clamping shoulder 22 and stop face 23. As shown in FIG. 7, clamping sleeve 3 is now slid in the direction of the arrow, counter to the direction of joining indicated in FIG. 5, until snap ring 4 comes to rest against second clamping shoulder 22. In the process, snap ring 4 first slides over the conical surface of undercut 24 and is thus automatically centered, together with clamping sleeve 3. In this position, clamping sleeve 3, via internal thread 34, is screwed together with external thread 11 of first component 1, as is shown in FIG. 1. In the process, support surface 20 of second component 2 comes to rest against surface 10 of first component 1. When clamping sleeve 3 is tightened, second component 2 is clamped against component 1 and is thereby secured on it. The snap ring is clamped between second clamping shoulder 22 and first clamping shoulder 35, which is formed by a section of annular groove 31.

[0018] The clamping assembly depicted here may be used in multiple forms. In no way is it limited to the exemplary embodiment described above, but, rather, may generally be used in those cases in which a first component is joined via a clamping sleeve and a snap ring to a second component having a cylindrical outer jacket. In a departure from the exemplary embodiment described above, it is possible to provide the clamping sleeve with an external thread and provide the first component with an internal thread. Moreover, stop face 23, for example, may be omitted if, in the assembly of clamping sleeve 3, snap ring 4 is pressed on using an appropriately designed tool, until it snaps into annular groove 32 of clamping sleeve 3. Moreover, it is possible to configure undercut 24 using a non-conical face. It is important for undercut 24, when viewed from support surface 20, to form, behind clamping shoulder 22, an open space which is used to hold snap ring 3, which is elastically compressed in the radial direction, so that clamping sleeve 3 is able to slide over snap ring 4 until the latter snaps into annular groove 31. 

What is claimed is:
 1. A clamping assembly, especially for use on a fuel injector of an internal combustion engine, comprising a first component (1) and a second component (2) that is fastenable to, and which has a support surface (20) that is supported against, the first component (1), having an essentially cylindrical outer jacket (21), the second component (2) being clampable via a clamping sleeve (3) that is slid onto the outer jacket (21) and that may be screwed together with the first component (1) and via a snap ring (4) against the first component (1), the snap ring (4) coming to rest against a first clamping shoulder (35), which is formed on the inner wall (33) of the clamping sleeve (3), and against a second clamping shoulder (22), which is formed on the outer jacket (21) of the second component (2). wherein the snap ring (4) is configured as a detent that elastically deflects radially, the outer jacket (21) of the second component (2) has an undercut (24), behind the clamping shoulder (22) in the axial direction as viewed looking out from the support surface (20), into which undercut the elastically deflecting snap ring (4) is able to deform radially inwardly so that the clamping sleeve (3), when slid onto outer jacket (21) of the second component (2), is guidable from the support surface (20) out over the snap ring (4), and the snap ring (4), which in the process is pretensioned against the inner wall (33) of the clamping sleeve (3), is able to be forced to snap into engagement in an annular groove (31) that is formed on the inner wall (33) of the clamping sleeve (3) as an opposing detent.
 2. The clamping assembly as recited in claim 1, wherein the second clamping shoulder (22) is disposed to the side of the support surface (20) and functions as an axial delimitation of an annular groove (27) in the second component (2), which has a depth greater than the wire cross-section of the snap ring (4).
 3. The clamping assembly as recited in claim 2, wherein the annular groove (27) of the second component (2) has a stop face (23) for the snap ring (4) situated opposite the second clamping shoulder (22).
 4. The clamping assembly as recited in one of claims 1 to 3, wherein the inner wall (33) of the clamping sleeve (3) has a peripheral chamfer (32) on its end that is slid onto the second component (2).
 5. The clamping assembly as recited in claims 3 and 4, wherein the chamfer (32) of the clamping sleeve (3) cooperates with the stop face (23) of the second component (2) in such a manner that the snap ring (4) that comes to rest against the stop face (23) when the clamping sleeve is slid on is able to deform radially inwardly, sliding into the undercut (24) along the chamfer (32). (FIG. 5)
 6. The clamping assembly as recited in one of claims 1 to 5, wherein the undercut (24) is formed by an essentially conical face that is directly adjacent to the second clamping shoulder (22).
 7. The clamping assembly as recited in one of the preceding claims, wherein the second clamping shoulder (22) is adapted to the shape of the wire cross section of the snap ring (4).
 8. The clamping assembly as recited in one of the preceding claims, wherein the wire of the snap ring (4) has a circular cross-section.
 9. The clamping assembly as recited in one of the preceding claims, wherein the annular groove (31) that is provided as an opposing detent encompasses the wire of the snap ring (4) in a press fit over approximately half of the perimeter.
 10. The clamping assembly as recited in one of the preceding claims, wherein the snap ring (4) that snaps into the annular groove (31) is clampable between the first clamping shoulder (35) and the second clamping shoulder (22) by screwing together the clamping sleeve (3) and the first component (1). (FIG. 7)
 11. The clamping assembly as recited in one of the preceding claims, wherein the clamping shoulder (3) has an internal thread (34) and the first component (1) an external thread (11). 